mdtls CVE-2026-93402

Exploitation requires the attacker to hold an active man-in-the-middle position between the mdtls-using client and its intended peer (e.g., adjacent-network attacker, hostile Wi-Fi/gateway, or DNS/ARP/BGP redirection), because the flaw only removes peer authentication - it does not by itself grant remote code execution or data access absent an interception point. The condition that enables it is intrinsic to the library (the verification result is discarded), so it applies to default use of any code path relying on mdtls for peer-identity checks rather than to a special configuration. What LIMITS exploitation: the attacker must be able to intercept/redirect the connection and present a substitute certificate; purely passive off-path attackers cannot leverage it. Authentication requirements cannot be confirmed from available data because no CVSS vector was provided.

This flaw is a classic peer-authentication bypass: 'mdtls discards the peer-identity verification result' means the library performs certificate/peer-identity validation but then ignores (throws away) the outcome, so a failed verification is treated the same as a successful one. This maps to CWE-295 (Improper Certificate Validation) and defeats the core security guarantee of (D)TLS - authenticating the remote peer. No CVSS vector, CVSS score, or CWE was supplied in the input, and there is no EPSS score, no CISA KEV listing, and no POC reference, so quantitative exploitation signals are absent and must be inferred. Real-world risk hinges almost entirely on whether an attacker can occupy a man-in-the-middle position on the network path: if they can, this is high impact (full impersonation of the trusted peer, breaking confidentiality and integrity of the channel); if they cannot, the flaw is latent. Because it silently disables authentication rather than crashing, it is unlikely to be noticed in normal operation, which raises the severity for security-sensitive deployments. The only corroborating signal is that the issue was reported/tracked by vendor:ubuntu, indicating it is a packaged software component under distro tracking rather than an unsubstantiated claim. Note the key uncertainty: the identity, version range, and deployment footprint of 'mdtls' cannot be confirmed from the provided data and should be verified against the Ubuntu security tracker and upstream advisory.

An attacker positioned on the network path (e.g., rogue Wi-Fi, ARP/DNS spoofing, or a compromised upstream hop) presents a forged or mismatched certificate to a client using mdtls. Because the library discards the peer-identity verification result, the connection is accepted despite the identity mismatch, letting the attacker impersonate the legitimate server and decrypt, read, or modify the supposedly authenticated traffic. No public exploit code is referenced in the input, but the flaw requires no special tooling beyond a standard MitM setup.